The escalating requirements for high density and performance associated with ultra large scale integration semiconductor wiring require responsive changes in interconnection technology, which is considered one of the most demanding aspects of ultra large scale integration technology. In addition, high performance microprocessor applications require rapid switching speed of semiconductor circuitry. The speed of semiconductor circuitry varies inversely with the resistance of the metal layer and inversely with the capacitance of the dielectric layer forming the interconnection pattern. As integrated circuits become more complex and the feature size and spacing become smaller, the speed of the integrated circuit becomes increasingly dependent on the capacitance and resistance of the interconnection pattern.
Prior efforts to increase the speed of semiconductor circuitry focused upon reducing the dielectric constant of material conventionally employed in forming dielectric interlayers. Silicon dioxide, the dielectric material conventionally employed in forming dielectric interlayers, has a dielectric constant of about 4. Prior efforts involve the development of materials having a lower dielectric constant than silicon dioxide, such as low dielectric constant polymers, teflon, aerogels and porous polymers.
It would be advantageous to employ such low dielectric constant polymers in combination with low resistivity metals, such as copper, silver, gold, and alloys thereof, in forming interconnection patterns. The combination of a low resistivity metal and low dielectric constant polymer would be expected to reduce resistance capacitance (RC) time delays. See, for example, Singer, "New Interconnect Materials: Chasing the Promise of Faster Chips," Semiconductor International, November, 1994, pp. 52, 54 and 56; and Adema et al., "Passivation Schemes for Copper/Polymer Thin-Film Interconnections Used in Multichip Modules," IEEE Transactions on Components, Hybrids, and Manufacturing Technology, Vol. 16, No. 1, February 1993, pp. 53-58.
However, the formation of a new reliable interconnection pattern comprising a low resistivity metal and low dielectric constant material is problematic in various respects. For example, aluminum, the interconnection metal of choice, inherently forms a passivation layer which protects aluminum from corrosion. However, low resistivity metals, such as copper, do not form a self-passivating layer. Moreover, copper ions rapidly diffuse through silicon causing damage to semiconductor components. In addition, most low dielectric constant polymers do not adequately adhere to metals. Accordingly, any attempt to form an interconnection pattern employing a low resistivity metal, such as copper, and a low dielectric constant polymer, would require the separate formation of a barrier/passivation layer to protect the metal layer from corrosion and prevent the diffusion of metal ions. In addition, a separate adhesion layer would be required. Such an interconnection pattern, manufactured by a damascene process, is schematically depicted in FIG. 1, and comprises a dielectric layer 10, which can be a low dielectric polymer, and a low dielectric constant polymer layer 11 formed thereon. The depicted interconnection pattern further comprises a low resistivity metal layer 12 comprising, for example, copper. In order to utilize a metal such as copper, barrier/passivation layer 13 is required, in addition to adhesion layer 14. Suitable barrier/passivation materials would include titanium, titanium nitride, tantalum, tantalum nitride, chromium, silicon nitride and silicon dioxide. The formation of such barrier/passivation layers, and separate adhesion layers, requires additional costly equipment, manipulative steps and materials, thereby decreasing throughput, increasing cost and further complicating the manufacturing process.
There exists a need for a simplified, cost effective technique to form an interconnection pattern comprising a low dielectric constant material and a low resistivity metal, such as copper, without forming separate barrier/passivation layers.